ON TUE CKYSTALLINB ROCKS OF THK LIZARD DISTRICT. 487 



splitting an intrusive dyke of gabbro and enclosed in it. Of this 

 rock the main mass is coarse, and in it foliation is either extremely 

 indistinct or absent. In the arm we find on one side medium- 

 grained gabbro, well foliated, passing into a compact gabbro, which 

 is but slightly streaked with a foliated structure, as indicated. The 

 serpentine, whether in the included block or in the main mass, shows 

 no sign of crushing. 



{(■) Yet more significant is another mass nearer the Carrick-Luz 

 dyke, the more important portion of which is represented in the 

 annexed diagram (fig. 6). The face of a dyke of gabbro forms a crag 

 about ten feet high, the lower edge resting ou serpentine. Above this 

 the mass for about two feet consists of a rather fine-grained gabbro, 



Fig. 6. — Foliation in (jabhro behuecn Compass Cove 

 and Spertiic Cove. 



1. Serpentine. 



2. Foliated gabbro. 



3. Partially foliated gabbro, 



4. Unfoliated gabbro. 



foliated or finely banded, " not unlike a piece of hornblende schist," 

 the bands being so thin that the mass, as a whole, is rather foliated 

 than striped. The next two feet consist of ordinary and foliated 

 gabbro, very irregularly mixed, but the streaks, as shown in the 

 diagram, have in places a distinct tendency to sweep round into the 

 fine foliated mass below. Lastly comes some half-dozen feet of 

 sporadically coarse or slightly foliated gabbro, in which occurs 

 now and then a thin wisp-like band of the fine foliated rock, resem- 

 bling that at the bottom, but not parallel with it. 



Microscopic examination of these foliated gabbros has not led to 

 any very definite results. The constituent minerals have been so 

 much altered since the structure was produced as to obliterate any 

 distinct indication of the agent by which it was caused. The 

 original plagioclastic felspar has been almost wholly replaced by 

 secondary products. Occasionally some diallage may be detected. 

 In the awjen-jiaser gabbros the larger grains of diallage still 

 remain comparatively unchanged, though they also often have a 



